Mechanical thermo-responsive actuating means



y 3, 1956 A. E. SCHWANEKE ET AL 2,753,419

MECHANICAL THERMORESPONSIVE ACTUATING MEANS Filed Dec. 14 1953zzvmvroas: 56/5 wazzeke red C :5 fiwazzejfe Qflrea a United StatesPatent MECHANICAL THERMO-RESPONSIVE ACTUATING MEANS Alfred E. Schwaneke,Northbrook, and Fred C. Schwaneke, Chicago, Ill., assignors to A-MCorporation, Chicago, Ill., a corporation of Illinois ApplicationDecember 14, 1953, Serial No. 397,850 8 Claims. (Cl. 200-137) Thisinvention relates to mechanical devices operated by the expansion andcontraction of a rigid body under the influence of temperature changes,and particularly to improvements in such devices wherein the physicalexpansion and contraction of a solid in response to temperature changesis utilized to operate some other means such as the switching element ofan electric thermostat.

The main objects of this invention are to provide an improved means forutilizing the physical expansion and contraction of a rigid body underchanging temperature conditions to actuate an operating arm; to providesuch a means for utilizing the lineal expansion and contraction of anelongated rigid body to actuate a lever arm integrally supported by thebody; to provide such a device in which dimensional changes of the bodyare greatly multiplied during translation to effectuate the function ofthe operating arm; to provide an improved actuating device in whichrelatively small dimensional changes in a rigid body caused bytemperature variations are translated into mechanical movement ofpractical operational use; to provide such a device that isoperationally more sensitive and accurate; and to provide such a devicethat is of simple unitary construction, easily fabricated, and of lowmanufacturing cost.

A specific embodiment of this invention is shown in the accompanyingdrawings, in which:

Fig. 1 is an elevational side view showing the principal elements of atemperature responsive actuating means embodying the invention.

Fig. 2 is a perspective view of the same.

Fig. 3 is a view similar to Fig. 1 showing an arrangement in which theoperating arm functions directly as a contact carrying switch member.

Fig. 4 is a plan view of a thermostat frame adapted to embody a devicesuch as that shown in Figs. 1 and 3.

Fig. 5 is a sectional view as taken on line 5--5 of Fig. 4 showing athermostat arrangement for using the device shown in Fig. 1.

Fig. 6 is a side elevation showing a thermostat arranged to use the formof actuating device shown in Fig. 3; and

Fig. 7 is a sectional view of the same as taken on line 7-7 of Fig. 6.

In the form shown in the drawings the improved actuating means comprisesthree principal elements, namely: a base member, or driving element 1,made of a soft material having a. high coefiicient of expansion; amotion translating member, or driven element 2, made of a materialhaving a relatively low coefficient of expansion; and an operatingmember or arm 3, which is actuated by the driven element 2.

The base member, or driving element 1, is preferably a solid elongatedbar having a flat bottom surface and adapted to be influenced by heat,through direct conduction, uniformly throughout its length. Any suitablematerial may be used for the member 1 which will withstand thetemperature to which it is to be subjected and which has a relativelyhigh rate of expansion and contraction under changing temperatureconditions. For example,

2,753,419 Patented July 3, 1956 brass or cobalt chromium steel may beused for this purpose.

The driven element or motion translating member 2 is preferably made ofa material having a low rate of expansion and contraction in response totemperature change, such as stainless steel or Invar, and is formed asan angle member, such as a forwardly oblique L, having a long leg and ashort leg, preferably with an acute included angle between them so thatwhen the ends of the legs rest on a common plane the short leg willstand substantially normal to the common plane.

In the form shown the remote ends of the legs of the driven element 2are set upon and integrally secured to the upper surface of the basemember 1 by means of laterally projecting feet 4 and 5, which are formedto lie flatly against the surface of the base member and which arepreferably welded thereto. Thus, upon any lineal expansion orcontraction of the base member 1, the long leg of the driven member 2,which is inclined upwardly from the base member, will act as a rigidstrut and the short leg 6, which stands substantially normal to the basemember, will be moved angularly about the axis of the angle corner 7between legs of the driven member. The axis of the angle corner 7 liesparallel with the plane of the base member 1 and at right angle to thedirection of lineal expansion and contraction thereof so that the corner7 functions as a stiff hinge between the legs and the short leg 6 isthereby principally affected, by any variation of the length of the basemember between the points where the feet 4 and 5 are secured, to changeits angular disposition relative to the plane of the base member.

The operating member or arm 3 is directly and rigidly secured by one endto the outer face of the short leg 6 of the driven element 2 by anysuitable means and is moved angularly with the short leg 6 about theaxis of the corner 7 upon any variation of the length of the basemember 1. The arm 3 is an elongated member, as shown, and the majorportion of its length extends outwardly across the corner 7 aconsiderably greater distance than the length of the short leg 6. Thusany lineal movement of the end of the short leg 6 at the plane of thebase member 1 is directly translated to the free end S of the operatingarm 3, in a swinging movement thereof about the corner 7, and ismultiplied in direct proportion to the relative lengths of the leg 6 andthe arm 3. In this way the relatively small changes in the length of thebase member caused by variations in temperature are increased ormultiplied to an extent sufficient for practical use, particularly whereoperative response to small temperature changes, or sensitivity, isdesired.

As shown in Figs. 1 and 3 the operating arm 3 is a substantially rightangle member having a short leg 9, secured directly to the short leg 6in parallel relation therewith, and a long leg disposed substantiallyparallel with the base member 1. In this manner the space occupied bythe actuating means or device is kept to a minimum without sacrifice ofthe movement multiplying function of the operating arm. It will beunderstood, however, that the disposition of the tree portion of theoperating arm may be as desired and in accordance with the manher inwhich the device is to be used.

In the arrangement of Fig. l, the arm 3 is intended to operate themoving blade of an electric switch, as in Fig. 5, and is provided withan operating button 10 of a suitable dielectric material, such asporcelain. In the arrangement of Fig. 3 the short leg 9 of the operatingarm 3 is suitably insulated from the driven member 2, by means of aninsulation plate 11 disposed between the legs 6 and 9 and by suitablyinsulating the mounting rivet. In this arrangement the arm 3 is intendedto function as the moving blade of an electric switch and carries acontact element 12 adjacent its free end 8.

means is illustrated in Figs. 4 to 7 inclusive, and in the form showncomprises. a one-piece frame havinga topplate 14 from which support legs15 and 16 dependon each side for suitable attachment to the base member1 of the actuating. means. As shown, the rearward legs 15 are staked tthe side margins of the base member 1 and hence rigidly fastenedthereto; The legs 16, however, which are located intermediatethe frameends, are engaged in marginal. notches 17 in the base member in such amanner as to permit relative movement in the longitudinal directionofthe base-member and yet secure the frame against lateral or verticalmovement relative to the base member. This is accomplished byunderbeveling' the inner edge of each notch 17 and then staking thebottom end of each leg 16' inwardly, as shown in Fig. 7, and by makingthe notches 1-7 of greater length than the legs 16.

As shown in-Figs. 4 and the thermostat is constructed toutilize-theactuatingmeans of Fig; l and in this arrangement the top plate 14 of theframe carries a pair of cantilevered switch blades 18 and E9; positionedso that the lower blade19 may be operated by the operating arm 3; Theswitch blades 18' and 19 are secured to the top plate 14 in the usualmanner by means of suitable terminal rivets 20 adapted for connectionwith conductor leads; not shown, and the blades have contacts 21 and12;.

respectively, adjacent their free ends for mutual coaction to open andclose an electric circuit between the blades.

In use this thermostat is mounted with the bottom surface of the basemember l in direct heat conducting engagement with the heated element tobe controlled, the frame being attached to suitable support members, notshown, by'means of the Wings 23 whichproject' from each side of theframe top plate 14.

Figs. 6 and 7 show a thermostat embodying. the actuating device of Fig.3. In this arrangement only the stationary switch blade 24 is carried bythe thermostat frame member 14, the operating arm 3 serving as themovable switch blade and the contact 12 thereof engaging the contact 25on the blade 24.

In the case of the thermostat of Fig. 5 the switch blade 19 is tensionedto bear away from the blade 18, toward the operating arm. 3, and anylineal expanding or contracting movement of the base member 1, inresponse to a temperature change, causes a proportionate angularmovement of the arm 3, to open or close the contacts 21' and I2, andhence controls the operation of. the electric heating means affectingthe base member 1. The arm 3, being a relatively stiff member, isdirectly responsive to any angular movement of the short leg 6 about theaxis of the angle corner 7 and because the base member 1 is of highexpansion rate material, whereas the driven member 2 is of a materialhaving a low expansion rate, only a relatively small change in thelength of the base member is required to produce an appreciable movementin the free end of the arm 3. Thus a relatively small temperature changewill cause opening and closing of the contacts 21-12 and the thermostatis comparatively quite sensitive.

In the case of either thermostat it will be seen that upon linealexpansion of the base member 1 of the actuating means, the short leg 6of the driven member 2 will be moved arcuately about the corner 7, inthe counterclockwise direction as seen in Figs. 5 and 6, soas to causethe free end' of the arm- 3 to lower and thereby open the contacts. Thisopen position is shown by the relation of theparts in Fig. 5". Uponcooling of the heated element,

however, the base member 1., contracts and moves the leg.

6, of. the driven element, in the. opposite direction so as tolift thearm 3 and'cause closing of, the contacts whereby the heating means againbecomes-energized. This closed.

positionis shown in,Fig. 6.

Adjustment of the thermostat for various ranges of operation isaccomplished by varying theposition of the stationary contact arm towardor away from the moving contact and any of several well known means maybe employed for that purpose. The adjustment means 26 shown is a commonarrangement and therefore need not be described.

The main advantages of this invention reside in the form and arrangementof the driven. element of the actuating means and the operating armcarried thereby whereby small amounts of expansion and contraction ofthe base member are greatly multiplied during: translation into usefulwork; and in the extremely simple construction of, the device which isnevertheless considerably more sensitive than arrangements heretoforeemployed.

Other advantages are to be found in the compact arrangement of theoperating elements of the device whereby a minimum of space is requiredfor its installation; and in the fact that the device is readilyadaptable for substantially any use where indication or control ofheattransmitted by direct conduction is desired.

Although two specific embodiments of this invention are herein shown anddescribed it will be understood that details of the constructions shownmay be altered or omitted without departing from the spirit of thisinvention as defined by the following claims.

We claim:

1. A device of the class described comprising a driving member of highexpansion material, a unitary driven memberof low expansion materialhaving two legs joining to form an angle, the remote ends of said legsbeing secured fast to said driving member in spaced relation, and anoperating arm secured to and extendingalong one of said legsacross andbeyond the corner formed by'the junction of said legs with each other.

2. A device of the class described comprising a driving member of highexpansion material, a unitary driven member of low expansion materialmade in the form of an angle having a long leg and a short leg theremote ends of which. are secured fast to said driving member, and anoperating arm mounted rigidly on the short leg of said driven member andextending therefrom across the corner formed by the angle junction ofsaid long and short legs.

3. A device of the class described comprising a driving member of highexpansion material, a unitary driven member of low expansion materialmade. in the form of an acute angle having a long leg and a short legthe member and extending therefrom across the corner formed by theanglejunction of said long and short legs.

4. A device of the class described comprising a. driving member of highexpansion material, a unitary driven member of low' expansion materialhaving two legs joining to form anangle, the remote ends of' said legsbeing secured fast to said driving member in spaced relation, one ofsaid legs being shorter than the other and disposed substantially normalto a plane common to the remote ends of both said legs, and an operatingarm mounted on said one leg'and extending therefrom across and beyondthe junction-of said legs with each other.

5. A deviceof the class described comprising an elon gated drivingmember of high expansion material, a unitary driven member of lowexpansion material extending lengthwise of said driving member andhaving a long leg and a short leg joining to form an acute angle, theremote ends of said legs being secured fast to said driving member inlongitudinally spaced relation, and an operating armvmonnted on saidshort leg and extending therefrom across the junction of said legs witheach other.

6'. A thermal-responsive actuator comprising an elongagted drivingmembermade of high expansion material, an, elongated driven memberv made oflow expansion ma? terial and bent intermediate its ends to form an acuteangle having a long leg and a short leg, said driven member beingdisposed lengthwise of said driving member and the remote ends of saidlegs being secured to said driven member in longitudinally spacedrelation, an operating arm mounted on said short leg and extendingtherefrom beyond the angle formed by the junction of said legs with eachother, said operating arm lying in a plane common to both said legs.

7. A thermal-responsive actuator comprising an elongated driving membermade of high expansion material, an elongated driven member made of lowexpansion material and bent intermediate its ends to form an acute anglehaving a long leg and a short leg, said driven member being disposedlengthwise of said driving member and the remote ends of said legs beingsecured to said driven member in longitudinally spaced relation, anelongated operating arm mounted by one end portion on said short leg andextending therefrom beyond the angle formed by the junction of said legswith each other, said operating arm lying in a plane common to both saidlegs and having the portion extending beyond said angle disposedsubstantially parallel with said driving member.

8. A thermo-responsive actuator comprising an elongated driving membermade of high expansion material, an elongated driven member made of lowexpansion material and bent intermediate its ends to form an acute anglehaving a long leg and a short leg, said driven memher being disposedlengthwise of said driving member and the remote ends of said legs beingsecured to said driven member in longitudinally spaced relation, anoperating arm mounted on said short leg and extending therefrom beyondthe angle formed by the junction of said legs with each other, saidoperating arm lying in a plane common to both said legs, and adapted tomove pivotally about said bent portion of said driven member away fromsaid driven member and said driving member upon contraction of saiddriving member.

References Cited in the file of this patent UNITED STATES PATENTS1,942,002 Romanelli Ian. 2, 1934 2,248,666 Fischer July 8, 19412,441,725 Smith May 18, 1948 2,627,565 Smith Feb. 3, 1953 2,664,483Broekhuysen Dec. 29, 1953

